fiber intake and risk of colorectal...

Vol. 7, 667-671, August 1998 Cancer Epidemiology, Biomarkers & Prevention 667

Fiber Intake and Risk of Colorectal Cancer’

Eva Negri,2 Silvia Franceschi, Maria Parpinel, andCarlo La Vecchia

Istituto di Ricerche Farmacologiche “Mario Negri,” 20157 Milan [E. N.,

C. L. V.]: Servizio di Epidemiologia, Centro di Riferimento Oncologico, 33081

Aviano, Pordenone [S. F., M. P.]: and Istituto di Statistica Medica e Biometria,

Universit#{224} degli Studi di Milano, 20133 Milan [C. L. V.], Italy

Abstract

The relationship between various types of fiber andcolorectal cancer risk was investigated using data from acase-control study conducted between January 1992 andJune 1996 in Italy. The study included 1953 cases ofincident, histologically confirmed colorectal cancers (1225colon cancers and 728 rectal cancers) admitted to themajor teaching and general hospitals in the study areasand 4154 controls with no history of cancer admitted tohospitals in the same catchment areas for acutenonneoplastic diseases. Dietary habits were investigatedusing a validated food frequency questionnaire. Oddsratios (ORs) were computed after allowance for age, sex,and other potential confounding factors, includingphysical activity and protein, fat, and carbohydrateintake. Fiber was analyzed both as a continuous variableand in quintiles. For most types of fiber, the OR of colonand rectal cancers was significantly below 1, and noappreciable differences emerged between the two. Whenthe unit was set at the difference between the uppercutpoints of the fourth and first quintile, i.e., the 80thand 20th percentiles, the ORs for colorectal cancer were0.68 for total fiber (determined by the Englyst method asnonstarch polysaccharides), 0.67 for soluble noncellulose

polysaccharides (NCPs), 0.71 for total insoluble fiber, 0.67for cellulose, 0.82 for insoluble NCPs, and 0.88 for lignin.When fiber was classified according to the source, theOR was 0.75 for vegetable fiber, 0.85 for fruit fiber, and1.09 for cereal fiber. The ORs were similar for the twosexes and the strata of age, education, physical activity,family history of colorectal cancer, and energy intake.Likewise, no appreciable differences emerged whensubsites of the colon and rectum were investigatedseparately. This study provides additional support for aprotective and independent effect of fiber on colorectal

Received 1/7/98: revised 5/26/98; accepted 6/5/98.

The costs of publication of this article were defrayed in part by the payment ofpage charges. This article must therefore be hereby marked advertisement in

accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

I This work was conducted within the framework of the Consiglio Nazionale delle

Ricerche (Italian National Research Council) Applied Project “Clinical Applica-

tions of Oncological Research” (Contracts 96.00759.PF39 and 96.0070l.PF39)

and with the contribution of the Italian Association for Cancer Research.

2 To whom requests for reprints should be addressed, at Istituto di Ricerche

Farmacologiche “Mario Negri.” Via Eritrea 62, 20157 Milan, Italy. Fax: 39-2-

33200231.

cancer, particularly for cellulose and soluble NCPs, andof fiber of vegetable or fruit origin.

Introduction

From the observation that rates of colon cancer were low in

some regions of Africa where the intake of fiber was high,Burkitt (1) hypothesized that fiber might protect against colon

cancer by increasing stool bulk, thus reducing transit time and

hence the contact of carcinogens in fecal material with the

colonic mucosa. Moreover, fiber can bind bile acids that pro-duce carcinogenic metabolites, and fermented fiber producesvolatile fatty acid that can protect against colon cancer either by

a direct anticarcinogenic action or by lowering the pH in the

bowel, thus preventing the conversion from primary to second-

ary bile acids, which seem to be carcinogenic (2).Fiber, particularly water-soluble fiber, can also delay the

absorption of starch, thus reducing the glycemic load and the

consequent postprandial hyperinsulinemia, which may promote

colon carcinogenesis (3).

These hypotheses are not mutually exclusive, and fibermay act in several ways to prevent colon cancer. There are

animal models showing different inhibitory effects of varioustypes of fiber on colon tumor development (4).

Several case-control studies have reported a protectiveeffect of fiber on colon and rectal cancer (5). A combinedanalysis of 13 case-control studies reported relative risks of

colorectal cancer of 0.79, 0.69, 0.63, and 0.53 for the fourhighest quintiles of intake compared to the lowest one (6). A

case-control study of over 2000 colon cancer cases from Cal-

ifornia, Utah, and Minnesota (7) also showed an inverse rela-tionship. The findings of cohort studies, however, are lessconsistent. The Nurses’ Health Study found a weak inverse

association only for fruit fiber (8), whereas in the Health Pro-fessionals Follow-Up Study, no clear relationship emerged be-

tween fiber and colon cancer risk (9). In the Iowa Women’sHealth Study, a nonsignificant inverse association between

dietary fiber and colon cancer was reported (10).Furthermore, various types of fiber differ in the extent to

which they increase stool bulk (and thus affect transit time) and

in fermentation. They also delay starch digestion to differentdegrees. Thus, it is important to analyze the effect of fiber

separately by type and origin (i.e., fiber from vegetables, fruit,or cereals). Previous case-control studies that looked separatelyat the source or type of fiber were often based on limited

numbers and yielded inconsistent results (1 1-14). In a study

conducted in Hawaii on about 1 200 cases, the protective effect

of fiber was limited to fiber from vegetables, whereas no clearrelationship emerged for fiber from fruit and cereals (15).

We investigated the issue using data from a large case-control study on colorectal cancer conducted in Italy (16). In1988-1992, mortality from colorectal cancer in Italy was 19.8/100,000 males and 13.0/100,000 females; incidence ranged

between 20/100,000 in southern Italy and 50/100,000 in north-ern Italy for males, and between 16/100,000 and 30/100,000 for

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668 Fiber and Colorectal Cancer

Table I Distribution of 1225 cases of co Ion cancer, 728 cases of re ctal cancer, a nd 4154 con trols according t a selected c ovariates, Ital y, 1992-1996

VariableColon cancers

No.

Rectal cancers

% No.

Controls

%No. %

Sex

Males 688 56 437 60 2073 50

Females 537 44 291 40 2081 50

Age group (yr)

<50 169 14 93 13 1079 26

50-64 583 48 339 47 1928 46

65-74 473 39 296 41 1147 28

Education (yr)”

<7 621 51 422 58 2276 55

7-Il 331 27 181 25 1156 28

�l2 267 22 122 17 693 17

Physical activity (at work)””

Low 444 36 231 32 1378 33

Medium 451 37 258 35 1476 36

High 330 27 239 33 1299 31

Family history of colorectal cancer’

No 1091 89 675 93 4008 96

Yes 134 II 53 7 146 4

Energy intake”

I ( lowest ) 374 3 1 228 3 1 1385 33

II 428 35 241 33 1384 33

Ill (highest) 423 35 259 36 1385 33

“ The sum docs not add up to the total because of some missing values.

I, Self-assessed score of physical activity.

‘ Family history in first-degree relatives.

‘I Sex-specific tertiles of controls. Upper cutpoints were 2397 and 3026 kcal for men and I 860 and 241 1 kcal for women.

females (17). Specific attention was paid to the separate effectof various types of fiber.

Subjects and Methods

The data were derived from a case-control study of colorectalcancer conducted between January 1992 and June 1996 in sixareas of Italy: (a) greater Milan, the provinces of Pordenone and

Gorizia, the urban area of Genoa, and the province of ForlI innorthern Italy (16); (b) the province of Latina in central Italy;

and (c) the urban area of Naples in southern Italy. The samestructured questionnaire and coding manual were used by cen-trally trained interviewers in all study centers. Data were

checked centrally for consistency and reliability. On average,less than 4% of cases and controls approached for an interview

refused to participate.Cases were incident (i.e. , diagnosed within 1 year before

the interview; mean, 2.5 months) histologically confirmed pa-tients with colorectal cancer, were less than 75 years of age, andwere admitted to the major teaching and general hospitals in the

area under surveillance. Overall, 1225 subjects with cancer ofthe colon (International Classification of Diseases 9, 153.0-153.9) and 728 subjects with cancer of the rectum (International

Classification of Diseases 9, 154.0-154.1), ages 23-74 years(median age, 62 years), were included. Controls were patients

with no history of cancer from the same catchment areas as thecases who were admitted to the same hospitals for acute non-neoplastic conditions unrelated to digestive tract diseases andnot associated with long-term modifications of diet. A total of4154 controls, ages 20-74 years (median age, 58 years), wereinterviewed. Of these, 23% were admitted for traumas (mostly

fractures and sprains), 28% were admitted for other orthopedicdisorders, 20% were admitted for acute surgical conditions,19% were admitted for eye diseases, and 10% were admitted for

miscellaneous other illnesses, such as ear, nose, and throat;skin; and dental conditions.

The questionnaire included information on sociodemo-graphic characteristics such as education and occupation, life-

time smoking and alcohol-drinking habits, physical activity,

anthropometric measures at various ages, a problem-oriented

personal medical history, and family history of cancer.

An interviewer-administered food frequency questionnaire

was developed to assess the usual diet during the 2 years

preceding diagnosis (for cases) or hospital admission (for con-

trols) and the intake of total energy as well as that of macro-

nutrients and micronutrients. The questionnaire included 78

foods, groups of foods, or dishes divided into 6 sections: (a)

bread, cereals, and first courses; (b) second courses (meat and

other main dishes); (c) side dishes (i.e., vegetables); (d) fruits;

(e) sweets, desserts, and soft drinks; and (f) milk, hot beverages,

and sweeteners. An additional section concerned alcoholicbeverages.

For a few seasonal vegetables and fruits, consumption in

season and the corresponding duration were elicited. At the end

of each section, one or two open questions were used to report

foods that were not included in the questionnaire but eaten at

least once per week. For 40 food items, the portion was definedin “natural” units (e.g., one teaspoon of sugar, one egg), and for

the remaining items, it was defined as small, average, or largewith the help of pictures. Dietary supplements were not con-

sidered, given their low level of consumption by this popula-

tion.To compute energy and nutrient intake, Italian food com-

position databases were used for about 80% of the food items

and integrated with other sources when needed (1 8). The re-

producibility and validity of the food frequency questionnaire

were satisfactory ( 19, 20).



Cancer Epidemiology, Biomarkers & Prevention 669

3 The abbreviations used are: NCP. noncellulose polysaccharide: OR, odds ratio:

Cl, confidence interval.

Table 2 o�t� of colon cancer an d rectal cancer according to the in take of various type s of fiber, Italy, 1992-1996

Type of fiberQ of intake in controls” Continuous [0 R (CI)]

Q2 Q3 Q4 Q5 Pso-P20 ‘unit 5-g unit

Total (Englyst) fiber”� (15.68) (19.63) (23.15) (27.86)

Colon 0.83 0.71 0.61 0.stY 0.69 (0.59-0.81) 0.86 (0.81-0.92)

Rectum 0.84 0.57 0.56 0.53� 0.67 (0.55-0.8 I ) 0.85 (0.78-0.92)

Colon and rectum 0.83 0.65 0.58 O.5I�� 0.68 (0.60-0.78) 0.85 (0.81-0.90)

Soluble NCP” (7.75) (9.76) (1 1.54) (13.89)

Colon 0.93 0.80 0.63 0.5ff 0.68 (0.58-0.80) 0.73 (0.64-0.84)

Rectum 0.91 0.58 0.66 0.55” 0.64 (0.52-0.79) 0.69 (0.58-0.83)

Colon and rectum 0.92 0.7 1 0.63 0.55” 0.67 (0.58-0.77) 0.72 (0.64-0.81)

Total insoluble fiber” (7.83) (9.81) (1 1.58) (13.93)

Colon 0.78 0.68 0.60 0.49” 0.71 (0.62-0.82) 0.76 (0.67-0.85)

Rectum 0.82 0.62 0.53 0.57� 0.71 (0.59-0.85) 0.76 (0.65-0.87)

Colon and rectum 0.80 0.65 0.56 0.51 0.71 (0.63-0.80) 0.76(0.69-0.84)

Cellulose” (413)d (5.35) (6.38) (7.78)

Colon 0.83 0.69 0.60 0.49� 0.68 (0.59-0.78) 0.59(0.49-0.72)

Rectum 0.83 0.56 0.56 0.50” 0.65 (0.55-0.87) 0.55 (0.44-0.71)

Colon and rectum 0.83 0.63 0.58 0.49” 0.67 (0.60-0.76) 0.58 (0.48-0.68)

Insoluble NCP” (3.56) (4.42) (5.16) (6.22)

Colon 0.87 0.69 0.67 0.62” 0.80 (0.69-0.92) 0.62 (0.47-0.83)

Rectum 0.89 0.61 0.61 0.68� 0.85 (0.71-1.01) 0.74 (0.53-1.03)

Colon and rectum 0.88 0.65 0.64 0.641 0.82 (0.73-0.92) 0.69 (0.55-0.85)

Lignin” (1.49) (1.85) (2.20) (2.68)

Colon 1.00 0.95 0.90 0.85 0.84(0.71-1.00) 0.49(0.24-0.98)

Rectum 0.79 0.74 0.69 0.82 0.95 (0.77-1.17) 0.81 (0.34-1.92)

Colon and rectum 0.91 0.85 0.81 0.83 0.88 (0.77-1.02) 0.59 (0.32-1.07)

Vegetable fiber’�-� (4.72) (6.10) (7.52) (9.51)

Colon 0.93 0.77 0.65 0.5ff 0.72 (0.63-0.82) 0.71 (0.62-0.81)

Rectum 0.73 0.73 0.57 0.61’ 0.80 (0.69-0.94) 0.79 (0.68-0.93)

Colon and rectum 0.85 0.75 0.62 0.58’ 0.75 (0.68-0.84) 0.74 (0.67-0.83)

Fruit fiber” (5.43) (7.93) (10.25) (13.38)

Colon 0.76 0.87 0.72 0.76k 0.88 (0.78-0.99) 0.92 (0.85-0.99)

Rectum 0.77 0.73 0.71 0.62� 0.87 (0.79-0.96) 0.87 (0.79-0.96)

Colon and rectum 0.76 0.80 0.71 0.7)1 0.85 (0.77-0.94) 0.90(0.85-0.96)

Grain fiber” (3.30) (4.26) (5.19) (6.54)

Colon 1.15 1.1 1 1.38 l.32� 1.05 (0.91-1.21) 1.08 (0.87-1.33)

Rectum 1.19 1.13 1.19 1.34 1.29(1.01-1.66) 1.25(1.01-1.66)

Colon and rectum 1.14 1.10 1.29 1.29” 1.09(0.97-1.22) 1.14 (0.95-1.36)

‘� Estimates from multiple logistic regression models including terms for center, sex, age, education, physical activity, and intake of various energy components, i.e. ,proteins,

fats, carbohydrates, and alcohol.

b � quintile. The reference category is the first (lowest) quintile. Quintiles are computed on the distribution of controls.

� The unit is the difference between the 80th and 20th percentiles of the distribution of controls. i.e., between the upper cutpoint of the fourth and first quintiles.

Consequently, the OR refers to a difference in intake between the 80th and 20th percentiles in the control distribution.

d The upper cutpoint of the quintile (in grams) is given in parentheses.

� Nonstarch polysaccharides.

fP < 0.01 (significance of the test for trend).

S Vegetable, fruit, and grain fibers were entered simultaneously in one model.

S p < 0.05 (significance of the test for trend).

Dietary fiber intake was derived using the Englyst proce-dure (21, 22), which measures fiber as nonstarch polysacchar-ides. A value was obtained for total fiber and for soluble andinsoluble fiber. A modification of the method allows cellulose

to be measured separately from insoluble NCPs.3 Values forlignin, a minor component of the human diet, were provided

separately. We did not include resistant starch in the computa-tion of total fiber because the amount depends on how each

food is processed and consumed (23), and related food corn-

position tables were not available. Fiber intake was also dividedaccording to the food from which it originated (i.e., vegetable,

fruit, or cereal).

Statistical Analysis. ORs and the corresponding 95% CIs

were obtained by means of multiple logistic regression models(24). The various types of fiber were entered in the models bothas quintiles of the distribution of controls and continuously. Inthe lafler case, two different measurement units were used: (a)the difference between the 80th and 20th percentiles of the

control distribution, i.e., between the upper cutpoints of thefourth and first quintiles; and (b) 5 g. Several models were fittedto the data, all of which were adjusted for age, sex, and center.Additional models included terms for education, physical ac-tivity, alcohol and energy intake, or fat, protein, and carbohy-drate intakes instead of energy. The inverse association be-tween fiber intake and colorectal cancer emerged only afteradjustment for energy intake, whereas models allowing for totalenergy or for its components (fat, protein, and carbohydrates)yielded similar results. The latter model was chosen for pres-entation.



670 Fiber and Colorectal Cancer

Table 3 ORs” and 95% CIs of colorectal cancer according to the intake of

various types of fiber in men and women, Italy. 1992-1996

OR (95% CI)Type of fiber -_______________

Men Women

Total )Englyst) fiber 0.66 (0.54-0.79) 0.67 (0.55-0.82)

Soluble NCP” 0.64 (0.52-0.77) 0.66 (0.54-0.82)

Total insoluble fiber 0.69 (0.59-0.82) 0.69 (0.58-0.84)

Cellulose 0.65 (0.55-0.76) 0.66 (0.55-0.79)

Insoluble NC�’ 0.81 (0.69-0.94) 0.81 (0.67-0.97)

Lignin 0.84 (0.70-1.02) 0.90 (0.72-1.12)

Vegetable fiber 0.69 (0.60-0.80) 0.78 (0.66-0.93)

Fruit fiber 0.87 (0.75-1.00) 0.82 (0.70-0.96)

Grain fiber 1.05 (0.90-1.23) 1.15 (0.96-1.38)

“ Estimates from multiple logistic regression models including terms for center,

age. education. physical activity. and intake of proteins. fats, carbohydrates, and

alcohol. Vegetable. fruit, and grain fibers were entered simultaneously in one

model. The unit for intake is the difference between the 80th and 20th percentiles

of the distribution of controls. i.e., between the upper cutpoints of the fourth and

first quintiles.

S Nonstarch polysaccharides.

Results

Table 1 shows the distribution of cases and controls accordingto sex, age, education, physical activity, family history of

colorectal caner, and tertiles of energy intake. Colon and rectal

cancer cases were older than controls and more frequentlyreported a family history of intestinal cancer and a higher

energy intake. Colon but not rectal cancer cases were more

educated than controls and reported a lower level of physicalactivity.

Table 2 presents the ORs according to the intake of various

types of fiber, both in quintiles and continuously. There was asignificant inverse association of total fiber intake and that of its

components with the risk of both colon and rectal cancer; theORs were very similar for the two cancers. The OR of colonand rectal cancers combined for a difference in intake of the

magnitude of the difference between the 80th and 20th percen-tiles of the control distribution was 0.68 for total fiber, 0.67 forsoluble NCPs, 0.7 1 for total insoluble fiber, 0.67 for cellulose,

and 0.82 for insoluble NCPs. The OR was also below unity forlignin, although not significantly (OR = 0.88).

Regarding the food source of the fiber, vegetable and fruit

fiber were protective; the corresponding OR for the two cancerscombined was 0.75 for vegetables and 0.85 for fruit fiber.Conversely, grain fiber was not associated with the risk of

colorectal cancer, and, if anything, the OR tended to be above1 . The results were consistent when the unit was set at 5 g for

all fibers. However, the ORs reflect the different absolute intakeof the various types of fiber, because these were highly corre-

lated. Consequently, a 5-g increase in the intake of ligninimplies a much greater increase in the intake of total fiber.

Table 3 presents the OR of colorectal cancer for thevarious types of fiber separately for men and women. The ORof total fiber was 0.66 in men and 0.67 in women, and for all

types of fiber considered, the ORs were very similar in bothsexes.

In Table 4, the association between total fiber intake andthe risk of colorectal cancer is analyzed in the strata of selected

covariates. No apparent differences emerged in the strata of ageor any of the other covariates considered, with the OR ranging

from 0.58-0.77 in the various strata. Likewise, no materialdifference emerged when the ORs were computed separatelyfor various subsites of the colon and rectum; the OR was 0.69for the right colon, 0.75 for the transverse and descending

Table 4 ORs” and 95% CIs of colorectal cancer, according to total fiber

intake, in strata of selected covariates, Italy. 1992-1996

Stratum OR (95% CI)

Age (yr)

<50 0.74 (0.56-1.00)

50-64 0.61 (0.50-0.73)

�65 0.75 (0.59-0.95)

Education (yr)

<7 0.64 (0.54-0.77)

�7 0.72 (0.60-0.88)

Physical activity (at work)

Low 0.64 (0.52-0.80)

Medium 0.70 (0.57-0.87)

High 0.66 (0.50-0.87)

Family history of colorectal cancer

No 0.66 (0.58-0.76)

Yes 0.77 (0.43-1.38)

Energy intake”

I (lowest) 0.58 (0.43-0.78)

II 0.59 (0.46-0.77)

III (highest) 0.76 (0.63-0.92)

“ Estimates from multiple logistic regression models including terms for center,

sex, age, education, physical activity. and intake of proteins, fats, carbohydrates,

and alcohol. The unit for fiber intake is the difference between the 80th and 20th

percentiles of the distribution of controls, i.e., between the upper cutpoints of the

fourth and first quintiles.

h Sex-specific tertiles of controls.

colon, 0.68 for the sigmoid colon, 0.60 for the rectosigmoid

junction, and 0.69 for the rectum (Table 5).

Discussion

This case-control study, one of the largest to date on fiber andcolorectal cancer, shows an inverse relationship between therisk of colorectal cancer and the intake of various types of fiber.The association was strong for fiber of vegetable origin, and in

fact, no association was observed for cereal fiber. No differ-ences emerged in the strength of the association between colon

and rectum or various subsites, sex and strata of age or otherselected covariates.

The use of hospital controls has been widely debated (24),and several strengths and weaknesses have been highlighted.Dietary habits of hospital controls may differ from those of the

general population, but we took great care to exclude from thecontrol group all diagnoses that might have involved any long-term modification of diet. On the other hand, the similar inter-view setting for cases and controls and the almost-complete

participation are reassuring, as are the satisfactory reproduc-ibility and validity of the food frequency questionnaire (19, 20).

With reference to confounding, further allowance for other

factors, including tobacco smoking and body mass index, didnot materially modify any of the associations.

Furthermore, the results of our study are in line with thoseof most case-control studies (5, 6, 25). They are of specific

interest, because they come from a Southern European popu-lation, for which little was known; moreover, they include

detailed information on various types of fiber.In this study, the protection conferred by cellulose and

soluble NCPs seemed slightly stronger than that conferred byinsoluble NCPs and lignin. However, plant foods contain thevarious types of fiber together, and in this study, the intakes of

various types of fiber were highly correlated. This makes itdifficult to distinguish between their effects. Vegetables and

fruit, however, contain proportionally more cellulose and sol-



Cancer Epidemiology, Biomarkers & Prevention 671

Table 5 Number of cases, OR,” and 95% Cl of cancer in various subsites of

the colon and rectum according to the total fiber intake,” Italy. 1992-1996

Site No. of cases’ OR 95% CI

Right colon 185 0.69 0.49-0.98

Transverse and I 88 0.75 0.53-1.06

descending colon

Sigmoid colon 442 0.68 0.53-0.87

Rectosigmoid junction 159 0.60 0.40-0.89

Rectum 569 0.69 0.55-0.86

‘, Estimates from multiple logistic regression models including terms for center.sex, age. education, physical activity. and intake of proteins, fats, carbohydrates.and alcohol. The unit for fiber intake is the difference between the 80th and 20th

percentiles of the distribution in controls.

b Nonstarch polysaccharides.

‘ For 456 cases of colon cancer, there were multiple subsites or the subsite was

not specified.

uble NCPs and less insoluble NCPs than do cereals. This study

found that only fiber from vegetables and, to a lesser extent,

fiber from fruit (but not that from cereals) protected againstcolorectal cancer. This lends support to the hyperinsulinemiahypothesis, because vegetables and fruit are richer in solublefiber, which is the most effective type in delaying starch ab-

sorption (26), and a clinical history of diabetes mellitus wasrelated to colorectal cancer risk in this dataset (27). The risk of

colorectal cancer in our study was directly associated with theintake of bread or pasta (16). In the Italian population, thecereals consumed are mostly refined grains; hence, the ratio

between starch and fiber intake from cereals may be much

higher than that in other populations. Thus, the (possible)promotional action of starch may totally overwhelm the pro-tective action of fiber. In a large study from California, Utah,

and Minnesota, high intakes of refined grains were associatedwith an increased risk of colon cancer, whereas the opposite

was true for whole-grain intake (7).Finally, our data do not suggest that the effect of fiber is

different in the two sexes (28), because the association of all

types of fiber with colorectal cancer was similar for both sexes.

Acknowledgments

We thank Judy Baggott, M. Paola Bonifacino, and the G. A. Pfeiffer Memorial

Library staff for editorial assistance.

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1998;7:667-671. Cancer Epidemiol Biomarkers Prev E Negri, S Franceschi, M Parpinel, et al. Fiber intake and risk of colorectal cancer.

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